BACKGROUND: Several angiographic patterns distal to severe M1 stenosis have been identified. We have assessed the relationship between these angiographic patterns and patient presenting symptoms, infarct patterns, perfusion status and outcome after recanalization. METHODS: Three angiographic patterns were retrospectively identified in 60 patients (M:F = 41:19; age range = 34-80 years, mean = 55) who underwent M1 stenting: (1) a normal pattern (n = 22); (2) a shift pattern of the borderzone of the anterior cerebral artery (ACA) and middle cerebral artery (MCA) down to the MCA side with decreased size of MCA branches (n = 16), and (3) a dilatation pattern of the MCA branches with slow flow and minimal shift of borderzone (n = 22). In addition, to analyze interreader agreement, we assessed the correlation between angiographic patterns and gender, presenting symptoms (stroke vs. TIA), infarct patterns on MRI (borderzone vs. non-borderzone infarcts), perfusion results and outcome after stenting by chi(2) or Fisher's exact test. RESULTS: Blind review revealed an excellent interreader agreement in the assessment of angiographic patterns (kappa = 0.681). The shift pattern was more common in women than in men (p = 0.007). The likelihood of stroke (25/60, 42%, p = 0.001), borderzone infarct (21/32, 66%, p = 0.010) and decreased perfusion (p < 0.001) were greatest in the dilatation pattern, followed by shift and normal patterns. The outcomes did not differ by angiographic pattern probably due to the low event rate (4/60, 6.7%) within 6 months. CONCLUSIONS: Patients with severe M1 stenosis had 3 different angiographic patterns, which correlated with presenting symptoms, infarct patterns and perfusion status. Differences in patterns may be related to variation in collateral circulation at the ACA-MCA borderzone and hypoperfusion status.